doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 1 Enhanced MAC proposal for high throughput. Tohoku University Hiroyuki Nakase and Hiroshi Oguma

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 2 Outline Background Frame aggregation for high throughput single link using UDP – Simulation – New MAC procedure –EDCF with CW definition for AP –Polling with static frame control –Polling with MAC frame aggregation of different IP link –Dual PHY method Development of PHY

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 3 Introduction Throughput of MAC SAP was limited by connection procedure based on CSMA/CA. SIFS, DIFS and backoff for every packet task group n is aiming to high throughput of more than 100Mbps. → New PHY and MAC proposal is needed

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 4 Proposal 1: Frame aggregation Frame format for aggregation –Aggregation of MAC frame to send same destination STA. –Aggregation Header is defined in addition to MAC header. –Aggregation header has informations of number of aggregation,

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 5 Frame structure Aggregation flag is defined in subtype field of MAC header. Aggregation header is defined. –Number of aggregation frames Subheader is added to each aggregated frame. –Length of frame MAC Header Aggregation Header SubHeader Frame 1 FCS Data Body SubHeader Frame2SubHeader Frame n Less than 9000 bytes SIGNALFrame BodyPreamble

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 6 Throughput with frame aggregation Simulation results Frame size of 1500x6 = 9,000 Byte by aggregation Point-to-point connection using UDP packet Wireless data rate is 324 Mbps Throughput of more than 180 Mbps was obtained

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 7 AP-STA Point-to-Point UDP packet ACK : 54Mbps SIFS: 16usec DIFS: 32usec Throughput using aggregation Frame aggregation is effective to improve MAC throughput in the case of P-P connection. 324Mbps (54 x 6ch) 216Mbps (54 x 4ch) 162Mbps (54 x 3ch) 274.8Mbps (84.8%) 191.2Mbps (88.5%) 142.9Mbps (88.2%)

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 8 MAC throughput using Scenario Scenario 1 of usage model –Conventional DCF –Enhanced DCF with unfair contention window setting –Proposal of employment of polling connection –Proposal of FDD mode using dual PHY

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 9 System throughput using EDCF PHY data rate of 216Mbps and 324Mbps CW setting of AP and STA is the same. Frame aggregation was employed. 6Ch, 4000Byte/CH Throughput: 32.4 Mbps 4Ch, 4000Byte/CH Throughput: 28.4 Mbps

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 10 System throughput using EDCF Unfair CW setting for advantage of AP –CWmin_AP= Mbps (Downlink : 49Mbps, Uplink: 1Mbps) at CWmin_STA= Mbps (Downlink : 47Mbps, Uplink: 0.3Mbps) at CWmin_STA=255 6Ch(324Mbps), 4000Byte/CH 4Ch(216Mbps), 4000Byte/CH Improvement of Throughput : 157% Improvement of Throughput : 168% Usage efficiency of PHY data rate is less than 60%

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 11 Proposal of Enhanced PCF Three Types of MAC procedure 1)Static Beacon Timing HCF ① Individual polling ② MAC frame aggregation for multicast polling 2)Advanced HCF with dual PHY Concept Improvement of system throughput AP acts full traffic control in BSS Suppression of overhead in low data rate traffic

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 12 Enhanced PCF with static beacon timing Beacon interval is fixed. (Ex. 10 msec) : Easy control with power saving Transmission available by only AP in guard duration Duration of alternate EPCF and EDCF Length of EPCF is defined by AP due to request AP broadcast information for EPCF using Beacon packet All STAs are controlled by AP even if STA adhoc communication

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 13 Example procedure Guard duration Beacon CF-end PCF Data Poll-request Poll-accept DCF Data EPCF durationEDCF duration STA-STA communication is also controlled by AP During EDCF duration, STAs are operated as standard DCF mode. Polling request is transmitted on the rule of DCF. EPCF duration is started from Beacon signal from AP.

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 14 Definition of frame format (I) Polling request and accept –STA sends a request frame to AP during DCF when STA has an application with fixed data rate streaming. –EX: HDTV, SDTV, VoIP, etc. –AP assigns on the polling list table for the STA, and send a acceptance frame to the SAT. Polling List Table AP has a polling list table for management of PDF duration. Data rate, sequence number, STA’s address, etc.

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 15 Numerical results of EPCF Scenario 1 10msec Beacon interval is assumed. –HDTV, SDTV, VoIP, MP3, VideoPhone is communicated under polling streaming. –Internet file transfer is under DCF. Necessary duration for polling : 4.8 msec Without re-transmission for packet error Estimated throughput more than 81Mbps. MAC efficiency is more than 96%.

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 16 Problem Waste duration of PHY preamble and SIGNAL field of 16+4usec in low data rate frame. –Ex: 0.096Mbps (VoIP) Preamble and SIGNAL: 20usec MAC Header + Data + 216Mbps: 16usec (36Byte + 120Byte + 4Byte)/(216Mbps) Solution :Reduce the number of PHY preamble –Merging downstream for low data rate!! MAC frame Aggregation for low data stream of < 1Mbps

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 17 Enhanced PCF with MAC frame merging Employment of MAC frame aggregation of AP-to-STAs frame during EPCF STA-to-AP frame is sending by reserved slot in Poll-accept packet Expansion of duration for EDCF due to suppression of EPCF overhead Guard duration Beacon CF-end PCF Data Poll-request Poll-accept DCF Data

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 18 Frame format Merge header has four fields of Frame Control, Duration, Source Address, BSSID and Sequence Control. PreambleSIGNALMerging MAC Header MAC SubHeader 1 Body + FCSMAC SubHeader 2 Body + FCS MAC SubHeader 3 Body + FCSFCS Frame Control 2 Duration 2 Source Address 6 BSSID 6 MAC SubHeader has fields of Sequence Number, Duration and Destination Address Duration 2 Destination Address 6 Sequence Control 1

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 19 Control Field Definition Frame Control Field –First 1 Byte is the same as conventional MAC header. –Number of aggregated MAC frames is represented. Sequence Control Field –Sequence number for identification –MAC information for individual terminal Protocol Version 2 Type 2 Subtype 4 Sequence Number 4 Retry 1 Pwr Mgt 1 Order 1 WEP 1 Number of Aggregation 4 Researved 4

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 20 Throughput Estimation (Scenario 1) 10msec Beacon interval is assumed. –HDTV, SDTV, VoIP, MP3, VideoPhone is communicated under polling streaming. –Internet file transfer is under DCF. Necessary duration for polling : 4.4 msec Without re-transmission for packet error Estimated throughput more than 82Mbps. MAC efficiency is more than 98%.

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 21 Dual PHY communication IFS for ACK, low rate AP-STA are wasted duration for 11n. –AP-STA and STA-AP connection are used the same frequency band : Time Division Duplex (TDD) In order to increase throughput, different band is used for STA-AP connection : Employment of Freqency Division Duplex (FDD) using 11a/b/g –Ack, low rate packet for STA-AP connection

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 22 Dual PHY protocol stack Definition of MAC sub-layer for merging different PHY PHY 11n PHY 11b/g/n MAC 11b/g/n MAC 11n MAC STA-AP AP-STA

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 23 Dual PHY communication Employment of 11b/g/n PHY for low data rate traffic of less than 1 Mbps High data rate of 11n PHY for large streaming such as HDTV, Gaming, etc. AP-to-STA streaming without IFS to achieve higher throughput. IFS is not needed for AP-STA ACK is transmitted immediately from STA

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 24 PHY and MAC implementation We have a national project to implement 5GHz high throughput WLAN terminal. –Development with Mitsubishi Electric Co. and NetCleus Systems Co. Band expansion based on 11a PHY format. –6 channels expansion available –Xillinx VertexIIPro was used for MAC implementation.

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 25 Block diagram of implemented modem Gbit Ethernet PHY LSIMAC Wireless LAN MAC Modulation Demodulation TX RF/IF RX RF/IF DAC ADC RJ45 Implemented on Virtex2Pro With dual processor of PowerPC450 14bit 160Msps 12bit 160Msps

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 26 Implementation of 5GHz modem

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 27 Implementation of modem MAC board : throughput of more than 100Mbps

doc.: IEEE /1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 28 Conclusion New MAC Proposal with effective polling procedure is indispensable for high system throughput using 11n. Our proposals are based on 1 Enhanced DCF with unfair contention window setting 2 Proposal of employment of polling connection 3 Proposal of FDD mode using dual PHY Every proposal has improvement of MAC-SAP throughput superior to conventional MAC procedure.